[clang] e0e07a7 - Fix detection of __attribute__((may_alias)) to properly look through
Richard Smith via cfe-commits
cfe-commits at lists.llvm.org
Wed Dec 11 14:04:48 PST 2019
Author: Richard Smith
Date: 2019-12-11T14:04:37-08:00
New Revision: e0e07a7e414e818788144511de0c6328285c43cd
URL: https://github.com/llvm/llvm-project/commit/e0e07a7e414e818788144511de0c6328285c43cd
DIFF: https://github.com/llvm/llvm-project/commit/e0e07a7e414e818788144511de0c6328285c43cd.diff
LOG: Fix detection of __attribute__((may_alias)) to properly look through
type sugar.
We previously missed the attribute in a lot of cases in C++, because
there's often other type sugar there (eg, ElaboratedType).
Added:
clang/test/CodeGenCXX/may_alias.cpp
Modified:
clang/lib/CodeGen/CodeGenTBAA.cpp
Removed:
################################################################################
diff --git a/clang/lib/CodeGen/CodeGenTBAA.cpp b/clang/lib/CodeGen/CodeGenTBAA.cpp
index 09de9591de7e..7d730cb1ed15 100644
--- a/clang/lib/CodeGen/CodeGenTBAA.cpp
+++ b/clang/lib/CodeGen/CodeGenTBAA.cpp
@@ -78,17 +78,18 @@ llvm::MDNode *CodeGenTBAA::getChar() {
static bool TypeHasMayAlias(QualType QTy) {
// Tagged types have declarations, and therefore may have attributes.
- if (const TagType *TTy = dyn_cast<TagType>(QTy))
- return TTy->getDecl()->hasAttr<MayAliasAttr>();
+ if (auto *TD = QTy->getAsTagDecl())
+ if (TD->hasAttr<MayAliasAttr>())
+ return true;
- // Typedef types have declarations, and therefore may have attributes.
- if (const TypedefType *TTy = dyn_cast<TypedefType>(QTy)) {
- if (TTy->getDecl()->hasAttr<MayAliasAttr>())
+ // Also look for may_alias as a declaration attribute on a typedef.
+ // FIXME: We should follow GCC and model may_alias as a type attribute
+ // rather than as a declaration attribute.
+ while (auto *TT = QTy->getAs<TypedefType>()) {
+ if (TT->getDecl()->hasAttr<MayAliasAttr>())
return true;
- // Also, their underlying types may have relevant attributes.
- return TypeHasMayAlias(TTy->desugar());
+ QTy = TT->desugar();
}
-
return false;
}
diff --git a/clang/test/CodeGenCXX/may_alias.cpp b/clang/test/CodeGenCXX/may_alias.cpp
new file mode 100644
index 000000000000..fbc4e22e731f
--- /dev/null
+++ b/clang/test/CodeGenCXX/may_alias.cpp
@@ -0,0 +1,25 @@
+// RUN: %clang_cc1 %s -triple %itanium_abi_triple -emit-llvm -O2 -disable-llvm-passes -o - | FileCheck %s
+// RUN: %clang_cc1 %s -triple %ms_abi_triple -emit-llvm -O2 -disable-llvm-passes -o - | FileCheck %s
+
+enum class __attribute__((may_alias)) E {};
+
+template<typename T> struct A {
+ using B __attribute__((may_alias)) = enum {};
+};
+
+template<typename T> using Alias = typename A<T>::B;
+
+// CHECK-LABEL: define {{.*}}foo
+// CHECK: load i{{[0-9]*}}, {{.*}}, !tbaa ![[MAY_ALIAS:[^ ,]*]]
+auto foo(E &r) { return r; }
+
+// CHECK-LABEL: define {{.*}}goo
+// CHECK: load i{{[0-9]*}}, {{.*}}, !tbaa ![[MAY_ALIAS]]
+auto goo(A<int>::B &r) { return r; }
+
+// CHECK-LABEL: define {{.*}}hoo
+// CHECK: load i{{[0-9]*}}, {{.*}}, !tbaa ![[MAY_ALIAS]]
+auto hoo(Alias<int> &r) { return r; }
+
+// CHECK: ![[CHAR:.*]] = !{!"omnipotent char", !{{.*}}, i64 0}
+// CHECK: ![[MAY_ALIAS]] = !{![[CHAR]], ![[CHAR]], i64 0}
More information about the cfe-commits
mailing list